1. Field
Embodiments of the present invention relate to a variable resistance memory device (or a resistance variable memory device) and a method for forming the same. More particularly, embodiments of the present invention relate to a variable resistance memory device including a resistance variable layer whose electrical resistance varies according to voltage or current applied thereto, which enables a switching operation between at least two different resistance states, and a method for forming the same.
2. Description of the Related Art
A variable resistance memory device has at least two resistance states and switches its resistance state according to an external input signal such as voltage applied thereto. A variable resistance memory device stores data by performing the switching operation. Examples of variable resistance memory devices include a Resistive Random Access Memory (ReRAM), a Phase Change RAM (PCRAM), a Spin Transfer Torque-RAM (STT-RAM), etc. Many studies have been made on the variable resistance memory device due to its simple structure and superior capabilities for retaining stored data even if the external input is no longer applied.
Among the variable resistance memory devices, ReRAM may include (i) a resistance variable layer formed of, for example, a Perovskite-based material or a transitional metal oxide, and (ii) upper and lower electrodes. In the ReRAM, a filament acting as a current path is formed or broken in the resistance variable layer repeatedly depending on a voltage level applied to the electrodes.
When the filament is formed, the resistance variable layer is in a low resistance state. In contrast, when the filament is broken, the resistance variable layer is in a high resistance state. The switching operation from the high resistance state to the low resistance state, and from the low resistance state to the high resistance state are called ‘set’ and ‘reset’ operation, respectively.